Linux下s3c6410的GPIO操作（4）

1、前面几篇中，有一篇层调用过一个这样的函数，如下：

static __init void s3c64xx_gpiolib_add_4bit(struct s3c_gpio_chip *chip)
{
chip->chip.direction_input = s3c64xx_gpiolib_4bit_input;
chip->chip.direction_output = s3c64xx_gpiolib_4bit_output;
}

此函数在arch/arm/plat-s3c64xx/gpiolib.c中定义，

/* The s3c64xx_gpiolib_4bit routines are to control the gpio banks where
 * the gpio configuration register (GPxCON) has 4 bits per GPIO, as the
 * following example:
 *
 * base + 0x00: Control register, 4 bits per gpio
 *        gpio n: 4 bits starting at (4*n)
 * 0000 = input, 0001 = output, others mean special-function
 * base + 0x04: Data register, 1 bit per gpio
 * bit n: data bit n
 *
 * Note, since the data register is one bit per gpio and is at base + 0x4
 * we can use s3c_gpiolib_get and s3c_gpiolib_set to change the state of
 * the output.
*/

此函数直接定义GPIO端口如A的某一个如A1为输入
static int s3c64xx_gpiolib_4bit_input(struct gpio_chip *chip, unsigned offset)
{
struct s3c_gpio_chip *ourchip = to_s3c_gpio(chip);

to_s3c_gpio(chip)函数源码如下：这个大家应该很熟悉

static inline struct s3c_gpio_chip *to_s3c_gpio(struct gpio_chip *gpc)
{
return container_of(gpc, struct s3c_gpio_chip, chip);
}
void __iomem *base = ourchip->base;基地址
unsigned long con;


con = __raw_readl(base + OFF_GPCON);
con &= ~(0xf << con_4bit_shift(offset));

其中     #define con_4bit_shift(__off) ((__off) * 4)

            #define OFF_GPCON   (0x00)
            #define OFF_GPDAT    (0x04)
__raw_writel(con, base + OFF_GPCON);


gpio_dbg("%s: %p: CON now %08lx\n", __func__, base, con);


return 0;
}

static int s3c64xx_gpiolib_4bit_output(struct gpio_chip *chip,
      unsigned offset, int value)
{
struct s3c_gpio_chip *ourchip = to_s3c_gpio(chip);
void __iomem *base = ourchip->base;
unsigned long con;
unsigned long dat;


con = __raw_readl(base + OFF_GPCON);读控制寄存器
con &= ~(0xf << con_4bit_shift(offset));
con |= 0x1 << con_4bit_shift(offset);设置数值，为写做准备


dat = __raw_readl(base + OFF_GPDAT); 读数据寄存器
if (value)
dat |= 1 << offset;
else
dat &= ~(1 << offset);


__raw_writel(dat, base + OFF_GPDAT);写数据寄存器
__raw_writel(con, base + OFF_GPCON);写控制寄存器
__raw_writel(dat, base + OFF_GPDAT);写数据寄存器

    这里有个疑问，为何要写两次数据寄存器？


gpio_dbg("%s: %p: CON %08lx, DAT %08lx\n", __func__, base, con, dat);


return 0;
}

2、同样还有

/* The next set of routines are for the case where the GPIO configuration
 * registers are 4 bits per GPIO but there is more than one register (the
 * bank has more than 8 GPIOs.
 *当某个GPIO端口的IO个数如H大于8个的时候，有两个控制寄存器
 * This case is the similar to the 4 bit case, but the registers are as
 * follows:
 *
 * base + 0x00: Control register, 4 bits per gpio (lower 8 GPIOs)
 *        gpio n: 4 bits starting at (4*n)
 * 0000 = input, 0001 = output, others mean special-function
 * base + 0x04: Control register, 4 bits per gpio (up to 8 additions GPIOs)
 *        gpio n: 4 bits starting at (4*n)
 * 0000 = input, 0001 = output, others mean special-function
 * base + 0x08: Data register, 1 bit per gpio
 * bit n: data bit n
 *
 * To allow us to use the s3c_gpiolib_get and s3c_gpiolib_set routines we
 * store the 'base + 0x4' address so that these routines see the data
 * register at ourchip->base + 0x04.
*/


static int s3c64xx_gpiolib_4bit2_input(struct gpio_chip *chip, unsigned offset)
{
struct s3c_gpio_chip *ourchip = to_s3c_gpio(chip);
void __iomem *base = ourchip->base;
void __iomem *regcon = base;
unsigned long con;


if (offset > 7)
offset -= 8;
else
regcon -= 4;
对大于8个的处理

con = __raw_readl(regcon);
con &= ~(0xf << con_4bit_shift(offset));
__raw_writel(con, regcon);


gpio_dbg("%s: %p: CON %08lx\n", __func__, base, con);


return 0;


}

static int s3c64xx_gpiolib_4bit2_output(struct gpio_chip *chip,
      unsigned offset, int value)
{
struct s3c_gpio_chip *ourchip = to_s3c_gpio(chip);
void __iomem *base = ourchip->base;
void __iomem *regcon = base;
unsigned long con;
unsigned long dat;


if (offset > 7)
offset -= 8;
else
regcon -= 4;同样


con = __raw_readl(regcon);
con &= ~(0xf << con_4bit_shift(offset));
con |= 0x1 << con_4bit_shift(offset);


dat = __raw_readl(base + OFF_GPDAT);
if (value)
dat |= 1 << offset;
else
dat &= ~(1 << offset);


__raw_writel(dat, base + OFF_GPDAT);
__raw_writel(con, regcon);
__raw_writel(dat, base + OFF_GPDAT);


gpio_dbg("%s: %p: CON %08lx, DAT %08lx\n", __func__, base, con, dat);


return 0;
}

这两个函数和上面的差不多，很简单。

到目前为止，整个arch/arm/plat-s3c64xx/gpiolib.c文件中的源码都被我们看完了，是不是挺简单的。

Linux下s3c6410的GPIO操作（5）的链接

Linux下s3c6410的GPIO操作（1）的链接

Linux下s3c6410的GPIO操作（2）的链接

Linux下s3c6410的GPIO操作（3）的链接